This invention relates to an actuator for controlling brake hydraulic pressure in a vehicle brake system, and solenoid valves used therein.
As shown in FIGS. 6 and 7, a typical actuator A for controlling brake hydraulic pressure in a vehicle brake system A comprises a hydraulic unit 1, a motor unit 2 mounted to one end of the hydraulic unit 1, and an electronic control unit (ECU) 3 mounted to the other end of the hydraulic unit 1.
Typically, the hydraulic unit 1 includes a reservoir 12, a pump 13, pressure increasing control valves 20 and pressure reducing control valves 30, which are all mounted in a housing 10 made of aluminum. The housing 10 is formed with a master cylinder port 14 and wheel cylinder ports 15 which communicate with the master cylinder port 14 through passages 16 in which the pressure increasing valves 30 are disposed. The wheel cylinder ports 15 also communicate with the reservoir 12 through passages 17 in which the pressure reducing valves 20 are disposed and through passages 18 in which the pump 13 and the pressure increasing valves 30 are disposed. This arrangement is shown in JP patent publication 2005-7955A.
The control valves 20 and 30 of the hydraulic unit 1 are solenoid valves. Typically, as shown in FIG. 8 and also in FIG. 2 of JP patent publication 2005-7955A, the pressure increasing control valves 30 each include a tubular yoke 31, a tubular bobbin 32 received in the tubular yoke 31, a current-excited coil 33 wound around the bobbin 32, and a movable core (plunger) 34 having a valve rod 35 and axially movably received in the bobbin 32 through a guide (valve housing) 36. A valve body 37 is disposed at the free end of the valve rod 35 and is moved into and out of contact with a seating surface 38a of a valve seat 38 by the core 34. In FIG. 8, numeral 4 indicates a terminal through which electricity is supplied to the coil 33, and 39 indicates a return spring for the valve rod 35.
Ordinarily, this type of actuator A includes eight or more hydraulic pressure control valves V (solenoid valves 20 and 30) that are arranged in a plurality of rows and a plurality of columns. In order to facilitate mounting of such control solenoid valves 20 and 30 (which are sometimes referred to as “control solenoid valves V” or “solenoid valves V”), as shown in FIG. 9, JP patent publication 09-118215A discloses an arrangement in which the yokes 31 of the respective eight solenoid valves V are integrally formed (see FIG. 3 of this publication). The yokes 31 have a substantially U-shaped cross-section and are arranged in two rows such that the yokes in each row are mirror images of the yokes in the other row with their openings facing the openings of the yokes in the other row. In each of the (eight) yokes 31, a coil 33 is mounted.
The conventional solenoid valve V shown in FIG. 8 has the tubular yoke 31 (circular in section). A plurality of such solenoid valves V are mounted in the housing 10 at predetermined intervals as shown in FIG. 10.
With an increase in the number of electronic devices used in today's vehicles, it is increasingly required to reduce the size and cost of individual parts thereof, including an actuator A mounted in the engine compartment for controlling brake hydraulic pressure. It is especially required to reduce the height H (see FIG. 6) of the actuator A.
In order to reduce the height H of the actuator A, in the arrangement of FIG. 10, the solenoid valves V are arranged at shorter intervals in the direction of the height H of the actuator. But even with this arrangement, it is often difficult to sufficiently reduce the height H of the actuator.